Hi to all. I have noticed some tripping of a Danfoss inverter VLT5000 with alarm 14 EARTH FAULT. After recycling the power and resetting the inverter it resumes normal operation. Is there any logical explanation for this? Earth fault is a short circuit between phase and earth and is something more or less permanent. Should i suspect the screnned cable between inverter and motor or should i expect a possible motor insulation failure?
Thanks in advance for your time.

 

Afternoon,

You don't mention if the installation is new or not. Has the inverter been running?

There are two things that I would check:
If the installation is new make sure that the incoming and outgoing cables are in the correct terminals - Trust me on this one, it will still power up wired up incorrectly.
The second is that the earth fault might not be the cable, that is to say don't discount it but I have had problems with water ingress into the motor windings causing this intermittent problem. The best possible solution is to remove the cabling from the motor (and more inportantly the drive) and megger both the cable and the motor windings.

Hope this helps.

 

i have the same problem. and i check the cables and the motor resistance and it was normal. so i asking if i can to give up on this fault(14 fault earth) to me it is not necessary.

 

Well, i had the same problem with earth fault and i checked all the cables i changed the inverter to other machine to check. and it appears that the problem is inside the inverter itself. any ideas what to do with that?

 

Yes, usually internal power supply circuit. Switch mode capacitors are favourite, or even opto-coupler isolation stage for driving output transistors. (note if fault had stayed with motor/cable and earth readings good suspect bearings on motor)